Separation of metals



Patented June 11, 1935 UNITED STATES PAT ENT j OFFICE" trio Main, Germany,

I Aktiengesellschaft; 1 Frankfort on"-the-.

N01lflravv ingr Application October 10; 1932; Serial No. 637;201}. In Germany'February 24,1927" 1 4 beast; (or :zs-aom I The present invention" relates to the separation of metals and more particularly to theseparation] in a substantially pure-state of iron, nickel,v cofbalt, molybdenum, tungsten,or"otherbase"'metals,' capable of forming carbonyls; from mixtures, such as ores, intermediate products andthelikecon'-- taining severalof these-elementsgin'a f reeprcom binedstate:

Numerous metallurgical processes are known for effecting such separation of metals, but all of them are attended" with the disadvantagethat they are very troublesome; usually requiring a very great number of different operations; and

often do not give satisfactory results vention makes use of a reaction whichh'as-not hitherto been thought of when aiming atasepa ration" of metals of the-kind hereinbefore defined. Use is made according tothepresent in= vention of the capacity of the aforesaid metals of reacting with carbon monoxide'or gases con- 1 taining carbon monoxide with the'formationof metalcarbonyls 1 forming metal carbonyls. I -lowever, difii'culties have often beenexperienced in carrying through this reaction, due on the one hand-tothefact'that some metallic materials of the aforesaidkind remetal carbonyls are very liable to suffer decom position.- In view of thisyit hasb-eencus tomary to select rather specific conditionsfor thepro duction of metal carbonyls; whichconditionsvary substantially; more particularly'as'to temperaturey and pressure,- for each of the" various metal car bonyls to 1 be produced! It would therefore seem impossible to find outconditions under which a plurality of metals, eachof which-is capable of forming a metal carbonyl, can be convertedsimultaneou'sly into the 1 corresponding in'etaFcap' bonyls with a satisfactory yield and at-aispeed of reaction which allows of 1 work{ on an} indus-- trial scale. a

Contrary toexpectatiom we have V the formation of metal carbonyls can-b'carried through successfully within a ver-y broad. range-"- of temperatures and pressures. It is this dis covery that the process according to-the present invention is basedupon. 1

bonyls.

Now; the process according, toithe-present infound that carbonyl scan be recovered separately; in a very simple manner, and? practically completely,. from mixtures containingseveralof' them; even, for example,.,from verylow-gra'de ores; by'treatin'g the mixtures, after; if necessary, a suitable prepara"-' tory treatment; with carbon" monoxide; and sepalrating the metals by way of the resulting car- The method ofiworlsing according to the present invention consists in allowing the carbonyl'compoundsto' be fbrinedsimultaneously; if

desired after' a suitable prelinnnarytreatment of the initial; material; preferably under elevated" pressure, at an elevated'temperature, whichgen erallyranges betweenabo'ut" 50" and about 400 1 0;, but'whi'ch may also be outside this range, since it depends on the pressure of. the carbon monoxide, andthen separating'them by fractional dephle'gmationffractional distillation or other" suitable method; after whiclrthey are decomposed into pure metals and? carbon monoxide. All of these methods of separation of" the carbonyls are equivalents for the purpose of the present in:

l, ventionf and; are hereinafter referred to for the It hasbeen' known priorto the'present'inven tion that the aforesaidkmetals are -capable of sake of brevity as fiactiontting';

According" to the present invention, all' substances which contain several metalscapableof forming carbonyls as-for. example oxidic, sulphidic, and arseniferous ores, metallurgical intermediate or wasteproducts; scrapings; sweepn' s; andfispeiss," can be treated. All that is necessary to ensure; by suitablepreliminary treatment, such'as roastihgf and reduction, that the metals are 'pre'sent in the material to be treated-with carbonmonoxide ina reactive form;

We shall now-proceed to explain more in detail the'conditi'ons underwhich we" carry through the formation of the-"metal carbonyls;

'I his reaction maybec'arried" through even at atmospheric pressures, though as a rule the" use of hi'gher pressuresflis advantag ous, because 'thentlie speedof" reaction is greater and there is less risk of a decomposition of the" metal carbonyl'staking place. The upper pre'ssure limit is given only by the resistanceof the apparatus used, and thusQthe' process may be carried through at -pressures as higli as50, 100; 200, 500

or even more atmospheres.

Ashasbeenpointed out' above, the temperature usuallyrangesbetweenabout 50 and about 400 CL The lower temperatures within this range: are used when treating materials which readily react with carbon monoxide, whereas higher temperatures within the order specified are employed for initial materialswhich reac't rather difficultly: In the case "of difficultly re- -pheres.

acting initial materials it is also advisable to use very high pressures.

We shall now explain more in detail by way of some specific examples, how the production of the metal carbonyls may be carried through in the process according to the presentinvention. 1

Example 1 a. A material containing the oxides of iron and nickel in addition to calcium sulphate is reduced by means of hydrogen at temperatures below 500 C., whereafter it contains 20' per cent, by

weight, of iron and 20 per cent of nickel. This and under a pressure of 200 atmospheres. Within an hour 98 per cent, of the materialis converted into the corresponding carbonyls.

Example 2 (1. A material containing l2 per cent of iron, 6 per cent of nickel and 6 per cent of cobalt in a reactive form in addition to gangue is'treated with a stream of carbon monoxide at 200 C..andv

under a pressure of 200 atmospheres. .90 per cent of the material is converted intogthe corresponding carbonyls in the course of 8 hours.

b. The same initial material is treated with a stream of carbon monoxide at 240 C. and under a pressure of 1000 atmospheres. In thiscase 90 per cent of-the' material is converted intothe corresponding carbonyls in the course of- 4=.'hours.

In these two experiments a mixture offmetal carbonyls is first obtained which is comparatively rich in the carbonyls of iron and nickel, whereas later a carbonyl mixture comparatively1rich in cobalt carbonyl is formed' Example 3 a. Any initial. material which has been subjected to reduction and then contains 10 per cent of metallic iron; 22.5 per cent of metallic nickel and 40 per. cent, of metallic molybdenum is acted upon with a stream of carbon monoxide at 200 C. and under a pressure of 200 atmos Thereby per cent of the .iron and nickel and l per cent of -.the molybdenum is converted into the corresponding carbonyls.

b. The same initial material is treated with a stream of carbon monoxide at 220 C. and under apressure of 200 atmospheres. Thereby 85per cent of -the iron and nickel and 5 per cent of the molybdenum is converted into, the corresponding carbonyls. w 1 V c. The same initial material is acted upon with a stream of carbon monoxide under apressure of 200 atmospheres, while slowly. increasing the temperature from 220 to 300 (3., at the samev rate as. the formation of: the carbonyls'tends to decrease At temperatures above 240 C. only small amounts of the carbonyls of iron and selected so that the material of lowest reactivity acted upon with a stream of carbon monoxide at 200? 0.,

reacts with the carbon monoxide at a satisfactory speed. The same applies to the speed of the gas current and its percentage in carbon monoxide, in case a gas mixture containing carbon monoxide is used. Under such conditions also the more reactive metals are converted-in a satisfactory, manner. It is only when, one component of the initial material is particularly reactive, whereas another component has a very low reactivity,,that it is preferable to slowly increase the reaction temperature, whereby two fractions of metal carbonyls are obtained, of which the one is comparatively rich in the carbonyl of the highly reactive metal, the, other being comparatively rich in the carbonyl of the other metal. Of course, care should be taken that practically no decomposition of *the carbon monoxide takes place, and it is for this reason that the reaction temperature should preferably not exceed about In ,case the metals capable of forming metal carbonyls are present in the initial material in aform'in which they donot react, or do not suflicientlyrapidly react, with carbon monoxide, the

initial material is first subjected toa suitable pretreatment in the manner which is well known in theart from the production of single metal carbonyls, and which therefore will not require detailed explanation. As examples of such preliminary treatments may be mentioned roasting followed, if necessary, by reduction in the case of, for example, natural sulphides such as nickel ores, or also oxidation and, if necessary, subsequent reduction.

.We now come to the explanation of that step in our process which has been referred to above as fractionating. As hasbeen set forth, this may be effected for example by fractional dephlegmation or fractional distillation. Regard must be had in this step to the properties of the several metal carbonyls, which are well known in the art, to avoid a decomposition of the metal carbonyls. Accordingly, the separation of the carbonyls by distillation is preferably effected in an atmosphere of stagnant or of flowing carbon monoxide which I will prevent decomposition, and if desired under elevated pressure.

Another method of fractionating consists in effecting the separation ofthe metal carbonyls by freezing out, if desired in the presence of solvents,

in which latter case the separation is effected by I fractionalcrystallization. This method of fractionating is based upon the surprising discovery that the solubility of solid metal carbonyls in liquid metal carbonyls strongly decreases as the ing, and may then be decomposed to the'free metals either directly or preferably after any adhering liquid metal carbonyls have been removed by means of, preferably cooled, solvents. By the said method it is also possible to separate several solid metal carbonylssuch as those of cobalt and molybdenum, either simultaneously or one after the other, from one or more liquid metal oarbonyls, as for example mixtures of iron carbonyl and nickel carbonyl. Mixtures of solid metal carbonyls thus obtained may then be separated further for example by fractional distillation.

i In some casesaand especially wheri the mixture tov be separated contains large amounts o'imetal carbonyls of higher melting point such as cobalt carbonyl and only small quantities of metal carbonyls of low'melting point such as nickel carbonyl, it is advantageous to dissolve the mixture in solventssuch as benzenabenzine, tetrahydronaphthaleneorzcarbontetrachloride, and then tocrystallize the difiicultly soluble carbonyl or carbonyls'by cooling the solution. i 1

Fractionating may also be effected in any' other suitable mannerpasrfor example by fractional decomposition, :fractional absorption,fractional diffusion, fractional sublimation,jor also by explain thefractionating" stepfi" I r r \Erample4 The'following examples will serve to further A mixture of equal parts, by 'weight,zof iron carbonyl and nickel carbonyl'is heated at atmospheric pressureon a water bath kept at 80 C., while passing through a current of carbon monoxide. The vapors evolved are passed through a fractionating column. J At 28 C. practically pure nickel carbonyl distils off, pure ironcarbonyl being left in the *distilling'vessel.

l ExampZe5 'A mixture of 30 per cent, by weight, of cobalt carbonyl andx'70 per cent, by weight, of nickel carbonyl is heatedat atmospheric pressure on a water bath kept at '80? C.,.while passing through a current. of carbon! monoxide The vapors evolved arepassed through. a fractionating column. At 30 C. practically pure nickel carbonyl distils off, pure cobalt carbonyl being left in the distilling vessel.

. "Example6 A-mixture-of equal parts, by weight, of iron carbonyl and cobalt carbonyl is heated on a wa-. ter-bath in vacuo under apressure of 25 millimeters mercurycolum'n, while passing through a current" of carbon monoxide. The vapors evolved are passed-througha fractionating:col-' umn. At 30 C. practically pure ironfcarbonyl distils oif, cobalt carbonyl with only about 0.2

,per cent of iron carbonyl being left the. distilling vessel. q

. Example 7 .A mixture of 65 parts, by weight, of iron carbonyl, 30 parts,.by weight, of nickel carbonyl and 5 parts, by weight, of cobalt'carbonyl is filtered and then distilled at atmospheric pressure. The vapors evolved are passed through a fractionating column. At a 'temperature, in the dephlegmator 'of the column, of 42 C. pure nickel carbonyl distils over. The second frac tion which is obtained at 102 .0. consists. of pure iron carbonyl. The residue left, in the distillation vessel consists of cobaltand the difiicultly .volatile cobalt tri-carbonyl and contains, only small amounts of iron or iron compounds.

Example 8 A mixture of equal parts, .by'weight, of iron carbonyl and cobalt tetracarbonyl is heated-to 120. C. under a pressure of 20 atmospheresin a distilling vessel provided with a fractionating column, while passing through a currentof carbon monoxide. Pure iron carbonyl distils off,

cobalt tetracarbonyl,withlonly,about'0.3 per cent ofl iron carbonyl being left iii the distillation vessel. r

l Example!) 2 parts, by weight, of a mixture of 96 per cent, by .weight,, of cobalt carbonyl and 4 per cent, by weight, of nickel carbonyl are cooled to 12 below zero C. and are shaken twice each with 1 part of benzine likewise cooled to 12 below zero C. The benzine is poured 01f and. the solid cobaltcarbonyl obtained is freed from benzine by suction while excluding air. 7'7 per cent of the. cobalt carbonyl originally present are thus obtained in a crystallized form practically free from nickel. The remainder of the cobalt carbonyl can be recovered from the benzine solution by distilling oif the benzine and the nickel carbonyl in a current of carbon monoxide.

q-Ezwmple A slow current of carbonmonoxide is passed at 115; Cpand under a pressure of 10 atmospheres through a mixture of 40 parts, by weight, of cobalt carbonyl and' 60 parts, by weight, of iron carbonyl. A suspension of cobalt and cobalt tricarbonyl in iron carbonyl is formed, which is then allowed to cool. i The solid constituents of the suspension are filtered. off and washedwith a little tetrahydronaphthalene. f Iron carbonylcontaining only small amounts'of cobalt carbonyl is obtained' The mixture of cobalt and cobalt tricarbonyl is subjected. to thermal decomposition, whereby metallic cobalt containing only traces of iron is obtained; 7

It will be seenfrom the foregoing that it is possible according to the-present invention to produce pure or practically pure metal carbonyls. In case the free metals are to be produced, the metal carbonylsiare then subjected to thermal decomposition inany known or suitable manner,

as for example according to the U. S. Patentsat 140 C. and under a pressure of 180 atmos pheres. The resulting reaction gas is passed througha receiver cooled=to -2 0 C. in which a mixtureof the-carbonyls of nickel, iron and cobalt condenses. During the distillation of this mixture in acurrent of carbon monoxide at ordinary pressure, nickel carbonyl, 'containing'2.5 per cent of iron carbonyLypas'ses over first, at from to 45 C.,-f011owed at from 45 to 60C., by a mixture of 66.8 per cent of nickel carbonyl and 33 per cent of iron carbonyl. The pure compounds are obtained by subjecting these liquid carbonyl mixtures to a second fractional distillation at atmospheric pressure. I

The residue from the first distillation consists of a mixture of cobalt tricarbonyl and cobalt tetracarbonyl, which is free from nickel and iron carbonyl, but contains small quantities of solid impurities carried over from the reaction furnace. It is converted into pure tetracarbonyl in a current of carbon monoxide at 150 C. and under a pressure 0f'200 atmospheres and thisproduct is,

ExampleIZ A metallurgical waste sludge containing cobalt, iron, and zinc is reduced with coal and then acted upon with carbon monoxide at 150 C. and under a pressure of 200 atmospheres. The resulting mixture of the carbonyls of iron andcobalt is withdrawn from the high pressure apparatus in the liquid state at 55 C. and collected in a receiver cooled by'means' of a mixture of ice and common salt. 75 per cent of the cobalt carbonyl crystallize from the liquid mixture and are separated therefrom by decantation and filtration by suction. The cobalt carbonyl thus obtained is practically pure.. The liquid portion of the carbonyl mixture may serve for taking up further batches of the carbonyl mixture withdrawn from the high pressure apparatus.

Example 1 3 An initial material containing 13 per cent of iron and 20 per cent of nickel in a reactive form is acted upon with a stream of carbon monoxide at between 200 and 250 C. and under a pressure of 300 atmospheres. 90 percent of themetals are converted into the carbonyls. The resulting carbonyl mixture is preheated to 60 C. and then 1 injected into the middle part of a bell-tray column provided with a dephlegmator regulated to reflux twice the amount of the distillate leaving the column. In the upper part of the column a tem-- perature of 42 C. .is maintained, while the temperature in the lower part of the column is 102 C. Pure nickel carbonyl is withdrawn at the top, and pure iron carbonyl at the bottomof the column. Only small amounts of a non-volatile residue are left which contains'mainly oil in addition to small quantities of metals and decomposition products of metal carbonyls; this residue may be worked up by combustion, reduction and conversion into metal carbonyls.

While we have explained the process according to the present invention by reference to specific examples, we Wish it to be understoodthat our Ven ion 13 not hunted thereto the Scope metals, which comprises acting on said material,

invention being defined by the appended claims.

What we'claim is: l

l. The process for the separate recovery of base metals capable'of forming metal carbonyls from a material containing at least two of such metals, which comprises acting on said material, while the same contains the .said metals in a form capable of reacting with carbon monoxide, with carbon monoxide under conditions causing reaction of at least two of said metals, thereby forming the carbonyl compounds of said metals simultaneously, and fractionating the resulting carbonyl mixture. Q I 5 2. The process for the separate recovery of base metals capable of forming metal carbonyls from a material containing at least two of such 7 metals, which comprises acting on said material,

while the same contains the said metals in a form capable of reacting with carbon monoxide, with carbon monoxide under conditions causing reaction of each of said metals, thereby forming ;the carbonyl compounds of said metals simul- Condensation is effected under taneously, and fractionating! the. resulting car-' bonyl mixture. v

3. The process for the separate recovery' of base metals, capable of forming metal carbonyls from a material containing at least two of such metals, which comprises acting on said material, while the same contains the said metals in a form capable of reacting with carbon monoxide, with carbon monoxide at a temperature between about 50 and about 400 C. under conditions causing reaction of at least two of said metals, thereby forming the carbonyl compounds of said metals simultaneously, and fractionating the resulting carbonyl mixture.

4. The process for the separate recovery of base metals capable of forming metal carbonyls from a material containing at least two of such metals, which comprises acting on said material, while the same contains the said metals in a form capable of reacting with carbon monoxide, with carbon monoxide at a temperature between about 50 andabout 400 C. under conditions causing reaction of each of said metals, thereby forming the carbonyl compounds of said metals simultaneously, and fractionating the resulting carbonyl mixture.

5. The process for the separate recovery of base metals capable of forming metal carbonyls from a material containing at least two of such metals, which comprises acting on said material, while the same contains the said metals in a form capable of reacting with carbon monoxide, with carbon monoxide under conditions causing reaction of each of said metals, thereby forming the, carbonyl compounds of said metals simultaneously, and fractionally distilling the resulting carbonyl mixture.

6. The process for the separate recovery of base metals capable of forming metal carbonyls from a material containing at least two of such metals, which comprises acting on said material, while the same contains the said metals in a form capable of reacting with carbon monoxide, with carbon monoxide at a temperature between about50 and about 400 C. under conditions causing reaction of each of said metals, thereby formingthe carbonyl compounds of said metals simultaneously, and fractionally distilling the re-.

sulting carbonyl mixture. 7

7. The process for the separate recovery of base metals capable of forming metal carbonyls from a material containing at least two of such while the same contains the said metals in a form capable of reacting with carbon monoxide, with carbon monoxide under conditions causing reaction of each of said metals, thereby forming the carbonyl compounds of said metals simultaneously, and fractionally distilling the resulting carbonyl mixture in an atmosphere of carbon monoxide.

8. The process for the separate recovery of base metals capable of forming metal carbonyls from a material containing at least two of such metals, which comprises acting on said material, while the same contains the said metals in a form capable of reacting with carbon monoxide, with carbon monoxide at a temperature between about 50 and about 400 C. under conditions causing reaction of each of said metals, thereby forming the carbonyl compounds of said metals simultaneously, and fractionally distilling the resulting carbonyl mixture in an atmosphere of carbon monoxide.

9. The process ofseparating iron, nickel and cobalt from materials containing the same, which comprises treating said materials to place the above metalsin a condition in which they will react with carbon monoxide, passing carbon monoxide over the so-treated materials at a-temperature of' about 140 C. and a pressure of about 180 atmospheres, cooling the resulting gas mixture to condense the carbonyls of said metals, and subjecting the condensate toa fractional distillation to separate the iron, nickel and cobalt carbonyls respectively. a

10. The process as defined in claim 9 wherein the fractional distillation is effected by distilling ofi nickel carbonyl at a temperature of from 20 to 45 C. and then distilling off the remaining nickel carbonyl and the iron carbonyl ata temperature of from 45 to 60 C. in a stream of carbon monoxide.

11. The process for the separate recovery of base metals capable of forming metal carbonyls from a material containing at. least two of such metals, which comprises acting on said material, while the same contains the said metals in a form,

capable of reacting with carbon monoxide, with carbon monoxide under conditions causing reaction of each of said metals, thereby forming the carbonyl compounds of said metals simultaneously, and'fractionally crystallizing the resulting carbonyl mixture.

12. The process for the separate recovery of base metals capable of formingmetal carbonyls from a materialcontaining at least two of such metals, which comprises acting on said material,

while the same contains thesaid metals in a form J While the same contains the said metals in a form capable of reacting with carbon monoxide, with carbon monoxide under conditions causing reaction of 'each of said metals, thereby forming the carbonyl compounds of said metals simultaneously, and fractionally decomposing the resulting carbonyl mixture;

'14. The process for the separate recovery of base metals capable of forming metal carbonyls from a material containing at least two of such metals, which comprises acting on said material,

while the same contains the said metals in aform capable of reacting with carbon monoxide, with carbon monoxide at a temperature between about 50 and about 400 C. under conditions causing reaction of each of said metals, thereby forming the carbonyl, compounds of said metals simultaneously, and fractionally decomposing the resulting carbonyl mixture. i f CARL MULLER.

LEO SCHLECHT. EMIL KEUNECKE. 

